The present invention relates to various improvements in recessed locks comprising a spring-latch and a bolt and provided with an emergency opening device.
Normally, in locks of the described type an inner handle and an outer knob are provided for the actuation of the spring-latch, whereas a key-operated cylinder is provided for the actuation of the bolt and can be replaced with a pushbutton device on the inside and with an electromagnetic release device on the outside.
However, in some cases, for example in the case of hotels, the possibility of simultaneously removing the spring-latch and the bolt from their locking position by acting from inside only on the spring-latch actuation handle is required. This need is imposed by safety reasons, in order to allow anyone who is locked in a room to rapidly exit when the necessary calm may be lacking, for example when a hazardous situation (fire) occurs, without having to first unlock the bolt with the key or pushbutton.
In locks which comply with these requirements (one of these is described, for example, in European Patent application No. 90100205.5 filed Jan. 5, 1990 by the same applicant), in order to prevent the actuation of the spring-latch from outside as well, the hub of the knob is disconnected from the hub of the handle.
In this manner it is possible to actuate only the spring-latch when the outer knob is actuated, whereas by actuating the inner handle both the spring-latch and the bolt are actuated.
Known locks with emergency opening have some constructive and operating problems.
First of all, the return force which restores the knob and the handle to their inactive position after actuation is obtained by means of the compression of the same spring. Consequently, considering that the knob offers a shorter lever arm than the handle, actuation of the knob entails a greater physical effort which is hardly negligible also in view of the fact that the spring must return to the inactive position the handle as well as all the other elements connected thereto that transmit the movement to the bolt.
Secondly, there is the need to modify the lock in order to make it suitable for doors which open inward or outward and in which not only the knob and the handle reverse their position but it is necessary to maintain the connection between the handle and the bolt in this reversed position.